Self-catalytic bath and method for the deposition of a nickel-phosphorus alloy on a substrate

Abstract

Disclosed are a self-catalytic bath and a method for the deposition of Ni-P alloy on a substrate. The bath comprises nickel sulfate, sodium hypophosphite as a reducing agent, acetic acid as a buffer and traces of lead as a stabilizer. It also includes a citrate used as a complexing agent associated with a gluconate used both as a catalyst and a stabilizer. The disclosed bath makes it possible to tolerate large quantities of hypophosphite and is relatively long-lived. Furthermore, it can be used to prepare large quantities of Ni-P alloy per liter of solution.

What is claimed is: 
     
       1. A self-catalytic bath comprising: nickel sulfate;   sodium hypophosphite as a reducing agent;   acetic acid as a buffer;   traces of lead as a stabilizer; and   a citrate used as a complexing agent and is associated with a gluconate that is used both as a catalyst and a stabilizer.   
     
     
       2. The bath according to claim 1, wherein the citrate is sodium tricitrate and the gluconate is sodium gluconate. 
     
     
       3. The bath according to claim 2, wherein, for a quantity of sodium tricitrate equal to 79 g/l, the bath includes about 229 g/l of sodium hypophosphite. 
     
     
       4. The bath according to claim 2, comprising; about 0.1 M NiSO 4  : 6H 2  O;   about 0.15 M Na 3  C 6  H 5  O 7  :2H 2  O;   about 0.33 M NaH 2  PO 2  :H 2  O;   about 0.092 M C 6  H 11  NaO 7  ;   about 0.024 M CH 3  CO 2  H;   traces of lead; and wherein the pH is set at about 5.5 and the temperature is set at about 85 to about 89° C.   
     
     
       5. The bath according to claim 3, comprising; about 0.1 M NiSO 4  : 6H 2  O;   about 0.15 M Na 3  C 6  H 5  O 7  :2H 2  O;   about 0.024 M CH 3  CO 2  H;   about 0.33 M NaH 2  PO 2  :H 2  O;   about 0.092 M C 6  H 11  NaO 7  ;   traces of lead; and wherein the pH is set at about 5.5 and the temperature is set at about 85 to about 89° C.   
     
     
       6. The bath according to claim 1, further comprising a deposition rate of at least about 12 μm/h. 
     
     
       7. The bath according to claim 6 providing deposited coatings having shiny appearance. 
     
     
       8. A bath according to claim 1 including a concentration of sodium hypophosphite to a concentration of Ni 2+  ions from nickel sulfate having a ratio of up to 3 to 4. 
     
     
       9. A self-catalytic bath comprising: nickel sulfate;   sodium hypophosphite as a reducing agent;   acetic acid as a buffer;   traces of lead as a stabilizer;   sodium gluconate as a catalyst and a stabilizer; and   complexing agent selected to reduce a concentration of free metal ions in the bath by several magnitudes and thus reduce electric potential in order to control kinetics of deposition of a nickel-phosphorous alloy.   
     
     
       10. A bath according to claim 9 wherein said complexing agent is sodium tricitrate. 
     
     
       11. A bath according to claim 10 wherein said sodium gluconate bas a concentration of up to 20 g/l. 
     
     
       12. A bath according to claim 10 wherein the pH is set at about 5.5 and the temperature is set at about 85° C. to about 89° C. 
     
     
       13. A self-catalytic bat comprising: nickel sulfate;   sodium hypophosphite as a reducing agent;   acetic acid as a buffer;   traces of lead as a stabilizer;   a citrate used as a complexing agent; and   a catalyst and a stabilizer, said catalyst including hydroxide functions capable of picking up H +  protons, thus preventing adsorption of the H +  protons on the surface of a substrate during deposition of a nickel-phosphorous alloy, said stabilizer preventing decomposition of the bath and increasing deposition of said nickel-phosphorous alloy.   
     
     
       14. A bath according to claim 13 wherein said catalyst and said stabilizer is sodium gluconate. 
     
     
       15. A bath according to claim 14 wherein said sodium gluconate has a concentration of up to 20 g/l. 
     
     
       16. A bath according to claim 14 wherein the pH is set at about 5.5 and the temperature is set at about 85° C to about 89° C.